Synthesis of 1- and 3-11C-labelled L-lactic acid using multi-enzyme catalysis

✍ Scribed by Peter Bjurling; Bengt Långström

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: French
• Weight: 307 KB
• Volume: 28
• Category: Article
• ISSN: 0022-2135
• DOI: 10.1002/jlcr.2580280409

✦ Synopsis

Abstract

The synthesis of 1‐ and 3‐^11^C‐labelled L‐lactic acid from the corresponding racemic 1‐ or 3‐^11^C‐labelled alanine using a multi‐enzymatic reaction route, is presented. DL‐[1‐^11^C]Alanine was synthesised by reacting sodium 1‐hydroxy‐ethyl sulfite with hydrogen [^11^C]cyanide, obtained from [^11^C]carbon dioxide, and ammonia followed by acid hydrolysis. DL‐[3‐^11^C]‐Alanine was synthesised by a methylation of a glycine derivative, N‐(diphenylmethylene)‐glycine tert‐butyl ester, with [^11^C]methyl iodide, obtained from [^11^C]carbon dioxide, and subsequent hydrolysis. The racemic 1‐ or 3‐^11^C‐labelled alanine was then converted to pyruvic acid, by D‐amino acid oxidase/catalase and glutamic‐pyruvic transaminase, which was directly reduced to L‐lactic acid by L‐lactic dehydrogenase in a one‐pot procedure. The total synthesis time was 40 minutes, counted from release of [^11^C]carbon dioxide. The decay corrected radiochemical yields were ca. 80% for L‐[1‐^11^C]lactic acid, based on hydrogen cyanide, and ca. 60% for L‐[3‐^11^C]lactic acid, based on carbon dioxide. The radiochemical purities were higher than 99% analysed by HPLC.